The dimensions of many different types of state of the art electronic devices are ever decreasing. To reduce the dimensions of electronic devices, the structures by which the microprocessors, memory devices, other semiconductor devices, and other electronic componentry of these devices are packaged and assembled with circuit boards must become more compact.
One approach to reducing the sizes of assemblies of semiconductor devices and circuit boards has been to minimize the profiles of the semiconductor devices and other electronic components upon carrier substrates (e.g., circuit boards) so as to reduce the distances the semiconductor devices protrude from the carrier substrates. Various types of packaging technologies have been developed to facilitate orientation of semiconductor devices upon carrier substrates in this manner.
Some semiconductor device packages are configured to be oriented substantially parallel to a plane of a carrier substrate, such as a circuit board. Conventionally, semiconductor device packages included several layers stacked one on top of another (e.g., a bottom layer of encapsulant material, a die-attach paddle of a lead frame, a semiconductor die, and a top layer of encapsulant material). In addition, the leads or pins of conventional semiconductor device packages, which electrically connect such packages to carrier substrates, as well as provide support for the packages, are sometimes configured to space the semiconductor device packages apart from a carrier substrate. As a result, the overall thicknesses of these semiconductor device packages and the distances the packages protrude from carrier substrates are larger than is often desired for use in state of the art electronic devices.
“Flip-chip” technology, or controlled collapse chip connection (C-4), is another example of an assembly and packaging technology that results in a semiconductor device being oriented substantially parallel to a carrier substrate, such as a circuit board. In flip-chip technology, the bond pads or contact pads of a semiconductor device are arranged in an array over a major surface of the semiconductor device. Flip-chip techniques are applicable to both bare and packaged semiconductor devices. A packaged flip-chip type semiconductor device, which typically has a ball grid array connection pattern, typically includes a semiconductor die and a substrate, which is typically termed an “interposer.” The interposer may be disposed over either the back side of the semiconductor die or the front (active) surface thereof.
When the interposer is positioned adjacent the back side of the semiconductor die, the bond pads of the semiconductor die are typically electrically connected by way of wire bonds or other intermediate conductive elements to corresponding contact areas on a top side of the interposer. These contact areas communicate with corresponding bumped contact pads on the back side of the interposer. This type of flip-chip assembly is positioned adjacent a carrier substrate with the back side of the interposer facing the carrier substrate.
If the interposer is positioned adjacent the active surface of the semiconductor die, the bond pads of the semiconductor die may be electrically connected to corresponding contact areas on an opposite, top surface of the interposer by way of intermediate conductive elements that extend through one or more holes formed in the interposer. Again, the contact areas communicate with corresponding contact pads on the interposer. In this type of flip-chip semiconductor device assembly, however, the contact pads are also typically located on the top surface of the interposer. Accordingly, this type of flip-chip assembly is positioned adjacent a carrier substrate by orienting the interposer with the top surface facing the carrier substrate.
In each of the foregoing types of flip-chip semiconductor devices, the contact pads of the interposer are disposed in an array that has a footprint that mirrors an arrangement of corresponding terminals formed on a carrier substrate. Each of the bond (on bare flip-chip semiconductor dice) or contact (on flip-chip packages) pads and its corresponding terminal may be electrically connected to one another by way of a conductive structure, such as a solder ball, that also spaces the interposer some distance away from the carrier substrate.
The space between the interposer and the carrier substrate may be left open or filled with a so-called “underfill” dielectric material that provides additional electrical insulation between the semiconductor device and the carrier substrate. In addition, each of the foregoing types of flip-chip type semiconductor devices may include an encapsulant material covering portions or substantially all of the interposer and/or the semiconductor die.
The thicknesses of conventional flip-chip type packages having ball grid array connection patterns are defined by the combined thicknesses of the semiconductor die, the interposer, and the conductive structures (e.g., solder balls) that protrude above the interposer or the semiconductor die. As with the flat packages, conventional flip-chip type packages are often undesirably thick for use in small, thin, state of the art electronic devices.
Thinner, or low-profile, flip-chip type packages have been developed which include recesses that are configured to at least partially receive semiconductor devices. While interposers that include recesses for partially receiving semiconductor devices facilitate the fabrication of thinner flip-chip type packages, the semiconductor dice of these packages, as well as intermediate conductive elements that protrude beyond the outer surfaces of either the semiconductor dice or the interposers, undesirably add to the thicknesses of these packages.
U.S. Pat. No. 5,639,695, issued to Jones et al. (hereinafter “the '695 Patent”), discloses another type of flip-chip type package, which includes an interposer with a semiconductor die receptacle extending completely therethrough. The '695 Patent teaches that the package may be formed by securing the semiconductor die directly to a carrier substrate and electrically connecting the interposer to the carrier substrate before the semiconductor die is electrically connected to the interposer. The semiconductor die, intermediate conductive elements that connect bond pads of the semiconductor die to corresponding contact areas on the interposer, and regions of the interposer adjacent the receptacle may then be encapsulated. While this method results in a very low-profile flip-chip type package, the package cannot be tested separately from the carrier substrate. As a result, if the package is unreliable, it may also be necessary to discard the carrier substrate and any other components thereon. Moreover, the packaging method of the '695 Patent complicates the process of connecting semiconductor devices and other electronic componentry to a carrier substrate.
Thus, there is a need for low-profile flip-chip type packages that may be tested prior to their assembly with a carrier substrate and without adding complexity to the process of assembling electronic components to the carrier substrate. A method for fabricating such low-profile flip-chip type packages is also needed.